


as long as we're going down

by nilchance



Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell, Choking, Dubious Consent, Ecto-Genitalia (Undertale), M/M, Sibling Incest, Soul Sex, Underfell Papyrus, Underfell Sans
Language: English
Status: Completed
Published: 2017-03-28
Updated: 2017-03-28
Packaged: 2018-10-11 22:15:30
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,471
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/10475592
Author URL: https://archiveofourown.org/users/nilchance/pseuds/nilchance
Summary: They fuck each other in a lot of ways, in the metaphorical and literal sense, but soul touching is too whatever for the suspicious, damaged bastards that they are.





	

Sans knows they're fucked up.

The world is fucked up. Kill or be killed, or whatever. But even by that low standard, he and Papyrus have a fucked up thing going on. He's not sure how it happened, like that proverb about boiling frogs that pretty much sums up Sans's view of the universe as a sadistic experiment with no controls. Bad science. God really ought to have his lab access revoked.

Yeah, so. He's a moody drunk and it's worse when he's drinking alone. When nobody's looking at him (okay, when _Papyrus_ isn't looking at him) he's like water without a glass to hold it: there's a mess and usually somebody's dick gets wet.

It'd be better if he could be at Grillby's, where there's noise and the probability of violence to keep him from thinking, but no, Papyrus had to get in a fucking snit and order him to wait for him at home. Undermining Papyrus's authority makes them both look weak. If they falter, there are plenty of folks around waiting to eat them alive.

Fair. They're both total dicks. Too bad for everybody else that Papyrus is the meanest motherfucker in Snowdin and getting meaner every day, and Sans is…

Thoughtfully, Sans hooks two fingers under the collar at his neck and tugs. It's not as good as when Papyrus does it.

There's a key in the door. Sans flings himself down on the couch, puts his booted feet on Papyrus's spot, and starts to snore. Look how much he doesn't goddamn care and how very much he isn't waiting up like Papyrus is his daughter on a prom date.

Normally after a meeting with Undyne Papyrus is all furious ranting at some (imagined) snub or gleefully smug at some (real) hint that his success got under her skin. Either one is loud. Tonight Papyrus is unnervingly quiet. The only sign of his approach is his heavy footsteps towards the couch.

Sans's nerves prickle. He keeps snoring, and plans to do so until Papyrus kicks the couch. When Papyrus climbs on top of him instead, the empty whiskey bottle slips from between Sans's fingers and hits the floor.

Papyrus frames Sans's body with his own, pinning him down, one long femur sliding between Sans's legs. Sans is immediately, humiliatingly good to go. His soul recognizes Papyrus and surges up, wanting. Doesn't even matter that Papyrus's hands are only on his wrists, squeezing so that the bones grind. Not enough to hurt him, but enough that it feels like he's digging grooves in the shape of his fingers.

"Wow." Sans grins up at Papyrus. "Hey, boss. Is that your legbone or are you happy to see me?"

"I'm never happy to see you." Papyrus smirks. "You're so easy. It's like calling a dog."

Sans can't exactly deny it. He grinds down into Papyrus's leg, bone on bone, unforgiving. "Heh. Woof."

Despite Papyrus's dismissive scoff, that hot, hooded look he's giving Sans is as clear a victory as a dart in a bullseye. It's as good as taking a deep drag on a cigarette. Heat starts to pool in the cradle of Sans's pelvis..

Papyrus takes both of Sans's wrists in one big hand, and fuck if that isn't a thrill. His other hand slides down to the front of Sans's shorts and squeezes. Not painfully, but a warning. "Make a cunt for me."

Sans doesn't care one way or the other what set of junk he uses, and Papyrus mostly doesn't either. They're both the kinds of guys who're cool with whatever they find in somebody's pants. But Papyrus has these moods, and him telling Sans to make a pussy for him to fuck means he's in a good mean one. That he has _plans_ , let's-wreck-Sans-until-he-cries plans.

It's like missing a step or having his soul turned blue, gravity swooping in on him. Because he's a dick, Sans says, "You gonna make me?"

Papyrus's eyes flicker red. Then he lets go of Sans's crotch and reaches up under Sans's hoodie instead, not even bothering to unzip it, and takes hold of his soul.

"Fuck!" Sans digs his heels into the couch, doesn't know if he's trying to get away or rub against Papyrus's body everywhere he can reach. The feeling of Papyrus gripping his soul is _loud_ , so much input that he can't tell if it hurts. It doesn't matter if he's trying to get away, it turns out, because he can't get out from under Papyrus if he tries. "Wait, fuck, wait--"

They fuck each other in a lot of ways, in the metaphorical and literal sense, but soul touching is too whatever for the suspicious, damaged bastards that they are. It's raw, like Papyrus has his fingers dug into Sans's skull through his eyesocket, an actual mindfuck.

A snatch of some human song hits Sans's brain: _like a virgin, touched for the very first time..._

He laughs, a jagged sound.

"Why would I do that?" Papyrus sounds bored, but through the connection between them he is broadcasting all possessive/protective. He won't break Sans because then he can't keep using him. "I'm only answering your question, brother. Yes, I'm going to make you."

Sans shudders and goes limp. He can feel the wires in his brain crossing, that tone in Papyrus's voice taking all the fight out of him. Papyrus wants something, and Sans wants to give it to him. It's that simple. Secondhand, he feels Papyrus's feral satisfaction as he buckles under.

His body is getting with the program, finally. He shifts his hips, angling their bodies together, and grinds slow against Papyrus's thigh. The friction is golden and sweet, and he groans.

"You'd rub off on my hip if I let you, wouldn't you," Papyrus murmurs. He is an unyielding cliff for Sans to wreck himself on. When Sans nods, Papyrus pulls his leg out of reach. Sans whines. "What, now your mouth won't work?"

"Yes, yes, okay, I totally would. C'mon. Come back." His body is humming away, alight. He can see his soul blazing through his hoodie. His magic should already be poured down into the cradle of his pelvis, a pussy or a dick or _something_ to be used. He tries to reach for his magic to do it himself, and Papyrus gives his soul a claustrophobic squeeze.

"What the fuck," he says.

"You had your chance to do it yourself. Obviously I have to do it for you."

"Can you even--" Sans shuts his mouth a couple seconds too late. That's the wrong question to ask Papyrus, and pretty stupid besides. Papyrus has scary control over his own magic and his hand on Sans's soul. Sans looks up into Papyrus's narrowed eyes and says, "Welp."

When Papyrus pulls Sans's soul out of his chest, it's like a dislocated shoulder: that pop and aching numbness down to the ends of his fingertips. Less pain and more visceral wrongness. He twitches, and Papyrus rubs his thumb over the surface, soothing and taunting at once. The pleasure is electric and ghostlike, like Papyrus is stroking his whole nervous system at once.

Papyrus raises the soul out from beneath Sans's hoodie and looks it over, silver fluid oozing over his fingers. Sans doesn't have much time for shame these days, but he wants to cup his hands over his soul and hide its nakedness. Its weakness.

Papyrus raises the soul to his mouth. For a dizzying instant Sans can almost see him taking a bite of it like an apple. Then Papyrus drags the flat of his tongue over it.

Silver runs over Papyrus's fingers and down his chin, the excess dripping down on Sans in hot little splatters. Raw magic, _his_ magic, and Papyrus is swallowing him down with wet, messy noises like he's got Sans spread open under his hands and is eating him out.  Sans can feel himself sliding down Papyrus's throat, getting weaker with every swallow, and he shudders. It's like bleeding to death, the same wooziness and spreading darkness, the heat of it. He sinks into the couch, panting, bones rattling.

In theory, he knows that Papyrus is going to stop. That Papyrus won't cripple or dust him, that he'll get his magic back after some sleep and some food, and it's no different than if Sans used up all his energy in an attack. In practice, all the alarm bells in his brain are screaming at him to struggle, to FIGHT, to call up his blasters while he's still got juice, to get Papyrus the fuck _off_ him. Survival instincts.

And he knows Papyrus can feel him fighting to stay still. Papyrus's approval is like a steadying hand at the back of his neck. The efficient way Papyrus is lapping him up, trying to get as much of his magic as fast as he can, goes more languid. Making it good for him.

And oh fuck, it's good for him. Sans would have come in sheer self-defense, but he has nothing to come _with_ , so he has to take it instead. There are tears on his face and he's riding the thin edge of blacking out when Papyrus stops. Papyrus is a long shadow above him, power radiating from him like heat off blacktop.

"I forget how much magic you have." Papyrus sounds controlled, damn him, though Sans can feel how much he's loving this, how hard his dick is, how much he wants to just grind Sans into dust. "You never do anything with it." Their entwined magic beats down like incoming violence, like war. "I ought to tear your soul out and keep it with me all the time. Use you like a battery. We could burn down the world."

Sans thinks, _I'd let you._

He doesn't say it, but it rings through the connection anyway. Papyrus's joy is savage. He runs the tip of his thumb over the point of Sans's soul, gives it a cruel flick. Sans makes a noise like he's dying.

Perversely tender, Papyrus rubs his cheek against Sans's soul. The stimulation drags a hiccupping sob from Sans's throat. "I'd come home every day or so to fuck you."

"Please," Sans says. He's not sure if he's begging Papyrus to let him come or to take his soul or to kill him right here. "Fuck, Pap, please--!"

Magic blossoms in his pelvis like blood from a wound. He's coming before he even really knows it's happening, coming with the cunt that Papyrus just gave him. It's horrifying and it's wonderful and he screams with it.

He might black out. For a few minutes it's all quiet in his head. All he knows is Papyrus's growl in his ear, and most of what he hears from that is "mine."

Eventually, he realizes that Papyrus has moved. This is less than ideal. His soul is back in his chest, under his ribcage, feeling wrong without Papyrus's hand around it. He cracks an eye open, and Papyrus is a blurry shape kneeling over his legs. There is a soft dark glow of magic, Papyrus's color and not his. Weird to see that in his own body, like somebody else's blood in his veins or the wrong colored eyes in his head. It's a little too big to fit comfortably in his bones, heavy in his hips, pressing him flat to the couch. Or hey, maybe he's just exhausted. He makes a noise like "hnngh?"

Papyrus doesn't look up. He's studying his handiwork. Almost negligently, he pushes Sans's femurs open until it aches and runs his thumb over the swollen lips of his pussy. That wakes Sans up fast.

"Hi there." Sans sounds like Papyrus has been fucking his throat for an hour. Half of Snowdin probably heard him. Fuck it, let them hear.

Papyrus licks the red slick off his thumb. His pants outline every generous line of his dick, the light of his magic like a cinder. Sans wants it so bad it aches.

"You called me Pap," Papyrus says. The soul connection is broken, a raw emptiness where Papyrus was, and Sans can't tell what he's thinking right now.

"Uh. Guess I did. I was kind of distracted."

He half expects Papyrus to hit him. Wouldn't be the first time. Wouldn't turn him off, either. He likes a little, or a lot of, pain. Sometimes it's easier than pleasure. He loves licking his blood off Papyrus's knuckles.

The moment stretches long. Papyrus is having an emotion, clearly, and not caring for it much. It'd be hilarious if it wasn't plain awkward.

"If you say it in public, I'll break your fucking jaw," Papyrus says finally.

"I wouldn't. I'm not that stupid." That would get them both killed, he means. After the great Christmas fistfight of '11, they try not to say each other's names at all. "Sorry or whatever. Can I suck your dick?"

Sans is soaked, fucking dripping, and Papyrus's fingers slide in so easy. Papyrus has big hands and he gives him three fingers, crooking them with vicious precision.

"Yeahhh," Sans sighs, arching under him. It's good to have something physical, pleasure in his bones instead of his soul, something real. Something less lonely. "That'll work."

All false concern, Papyrus says, "Tired already, brother?" The sweetness drops away. "I decide when we're finished."

"Sorry, boss," he says, trying for meek and failing because he's snickering. "Won't do it again, boss."

Papyrus hooks his fingers and drags Sans down the couch. Sans yowls, starts to grab for Papyrus, hears the warning growl and digs his nails into the upholstery instead.

Papyrus rubs his thumb across Sans's clit, rough and careless. It's like he has a fucking roadmap to Sans's nervous system, stroking right where it's good. But then, Sans isn't the one who shaped his magic this time around. Papyrus has the cheat codes here. Sans would tell him to go fuck himself, but Papyrus is pretty much doing it. Vain bastard is loving it, too.

Sans tries to ride Papyrus's hand, but Papyrus has a tight grip on his hipbone and Sans isn't going anywhere. He has to just take it.

"Break me open on your dick," he pants. He says some frankly ridiculous shit when he's getting fucked. At least this time he isn't calling anyone daddy or telling Papyrus to fuck him pregnant. "You made it. Bet it's real tight. C'mon and try it out."

"Call me that name again," Papyrus says.

"Wha--?" Sans takes a second to understand. When he does, he flushes hot and cold all over. It feels kinky to say his brother's name like he used to, back when they loved each other. "Pap."

Papyrus shudders, eyes almost closing. Then he starts to unbuckle his pants.

Fuck. Mouth watering, jaw aching like Papyrus's dick is resting on his tongue, Sans says roughly, "Fuck me, Pap, I need it."

With a rattling growl, Papyrus crawls between his spread legs. Papyrus has his pants on, just opened them enough to take his dick out. The zipper scrapes across Sans's femur with a noise that puts his teeth on edge. Papyrus slides his fingers out and wipes them on Sans's jacket, the douche, then takes his cock in hand. The fat head slides up and down Sans's slit, rubbing precome all over him.

Sans presses into Papyrus's dick as much as he can. The tip nudges just inside him, spreads him open. Sans gives a humiliating whimper and, apparently satisfied, Papyrus shoves into him hard.

This time Papyrus doesn't give him a second to adjust, just uses him like a warm hole to fuck. Every thrust pushes him up the couch.

"Yeah," Sans chants, "yeah, yeah, right like that, fucking give it to me, Pap, make it hurt. 'M yours."

Papyrus takes him by the collar, uses it for leverage. He's got Sans bent in half so that Sans can't get enough air. All Sans's words turn to dust. This time, when Sans grabs for him, Papyrus lets him.

"Good dog," Papyrus says in his ear.

And that's it, all he needed, he's coming like it'll kill him. He scratches up Papyrus's shoulders through his shirt, digging his fingers in between Papyrus's vertebrae where it's soft cartilage. Clenches down hard. He wants to wring Papyrus out, because fucked if he's going down alone. 

Spine bowing, Papyrus gives him what he wants. Papyrus makes the same throaty sound when he gets off as he does when he shanks somebody. Sans can feel hot pulses of Papyrus's magic hitting his spine, and he purrs.

Compared to his first skullfucking orgasm, the second one is sweet and long. He can't really feel his fingers when it's done, can't vouch for the solidity of his spine. Papyrus stays on top of him, his body both a weight bearing Sans down and a shield between him and the world. Sans could sleep like this, with Papyrus's dick still in him.

Papyrus lets go of Sans's hipbone first. Sans grumbles, and Papyrus tugs the collar tighter until Sans chokes. Exhausted as he is, he feels it all the way down to his clit, gets a little wetter on Papyrus's cock.

"I know what you need," Papyrus says, voice low. "Better than you do."

There are black shadows spreading in Sans's vision. He can't really breathe. He nods, leaning into the pressure so that it's a little harder. His body throbs. 

Papyrus releases him. Sans slumps back into the couch, sucking in air, and hisses as Papyrus pulls out. Patting him on the top of the head, patronizing, Papyrus climbs off the couch and goes into the kitchen. Without him, Sans feels like his body might drift up to the ceiling.

When he was a kid, he used to have nightmares about space. About how an astronaut who came untethered might drift off into the dark, nothing to do but wait for their oxygen supply to run out or the sun to bake them to death. A stupid thing to be scared of, considering that he's never going to even see the stars. They're all going to starve or kill each other down here.

He doesn't dream anymore.

His body stays where it's been put. He's feeling no pain, thanks to the miracles of whiskey and blood chemistry. His head is humming the same static frequency as the TV, a comfortable nothing.

Papyrus comes back with a glass in his hand and just looms over Sans for a minute, every inch of him a threat. His pants are zipped, belt closed, like nothing ever happened. No glow of magic. Untouchable.

Sans grins fuzzily at him. He can feel Papyrus's come sliding out of him. He doesn't know what he looks like, doesn't really _want_ to, but he knows it's the opposite of untouchable. Sloppily fucked? Wrecked party favor? Five minutes out from a fruit punch gangbang?

Papyrus sits and hands him the glass. "Drink it."

Sans does. It's water, not anything interesting, but Papyrus getting a cup of water after they're done fucking is practically a love letter. Of course, Papyrus waits until Sans's got his mouth full to say, "It's my magic, not yours. You're keeping that pussy until I decide to let it go."

Sans swallows and drops the empty glass on the floor, just to watch Papyrus’s blood pressure spike. Wipes his mouth with the back of his hand. "Yep. I figured."

"Could be days."

"Okay."

Papyrus is watching him, trying to see a reaction. "Everyone will see my magic on you. They'll know that I can fuck you whenever I want. Maybe I'll bend you over the bar at Grillby's so they can see what they can't have. They'll know who owns you."

"Heh. Everybody already does."

"Not everybody," Papyrus says.

Oh. Yeah, okay, that's what this is about.

Some city fuck came around and tried to grab Sans by the collar. The guy's boots were great once Sans knocked his dust out of them. Steel-toed, real quality shit. Papyrus hadn't even been in Snowdin, and Sans had it handled. There was no reason for it to get back to Papyrus. Of course Sans should've expected that it would.

He slants a look at Papyrus. It can go either way with him when Sans handles his own kills. Sometimes he's smug, like _look what my trained dog can do_. Sometimes he reams Sans out for stealing his kills.

Turns out there's a third option. Under that perpetual hardass sneer, Papyrus looks _young_. 20 and not as bulletproof as either of them want.

"Well." Sans grins with all his meanness in it. "Then I guess we'll fucking show them all, won't we, boss?"

After a second, Papyrus smiles back, and in it Sans can see the end of the world.

It's beautiful.


End file.
